Yeah it was a subtle find. Good catch. ITTR also posted it in this post:

Shash: "On the other hand, POET has entered into many of these types of LOI in the past...Silterra, Acellink"

Per Mika's recent presentation, it does seem Accelink has shifted from a development partner to potential customer (as listed on the "Sanan IC-POET Joint Venture Model" slide).

POET's relationship with Silterra, however, was not a "momorandum of understanding" or "letter of intent", but a true partnership. Silterra remains the key foundry for "commercial production of the Optical Interposer", as all IP related to the optical interposer will not be shared with POET's new joint venture and design and processing of the OI will not occur in China.

The mininimum duration of POET's partnership with Silterra is until April of 2021 and likely to extend beyond given Silterra's investment: "SilTerra has agreed to assist financially with the purchase of specialized semiconductor fabrication and testing equipment, as well as to share certain costs associated with facilities enhancements and installation of equipment for manufacturing the Optical Interposer."

https://poet-technologies.com/news/2018-apr-9.html